Photographic materials



Mq 2s, .1946.

J. A. H.THART l-:rAL 2,400,989

PHOTOGRAPHIC MATERIALS I Filed March s, 1945 FULLY ESTERIFIED v METHYL METHAORYLATE GELATTNO SILVER HALIDE LAYER 20% HYDRCLYSED METHYL METHACRYLATE 20% HYDROLYSED METHYL METHACRYLATE FULLY ESTERIFIED lMETHYL METHAGRYLATE` PAPER STYRENE IMPFIEGNA'T'EJV F IG'. '2

mumm

GELATINO SILVER HALIDE LAYER 20% MYDROLYSED METHYL METHAGRYLATE 4Fumar. EsTeRlFlso METHYL MeTHAcRYLATE -Pom/wma. cHLoRlDE INVENTRs John Hredlenr Hart BY and Edward W iamLee Patented May 2s, 1946 John Alfred Henry Hart and Edward William Lee, Ilford, England, assignors to Ilford Limited, Ilford,

England, a British company Application March 3, 1945, Serial No. 580,924

December 17, 1943 A l 7 Claims. (Cl. 95-9) In Great Britain This invention relates tophotographic materials and particularly to photographic elements comprising a gelatino layer. e. g. a gelatino'silver halideemulsion layer, carried on a hydrophobie support. f` s Photographic elements generally speaking comprise a gelatino silver-halide emulsion coated on a supporting sheet of paper, glass or cellulose derivative lm. In recent years there have been developed a'large number of synthetic colloid materials which can be used as supports for the silver halide emulsion. By selection from among such materials supports can be made which have physical characteristics rendering them suitable for special purposes. For` example, a sheet of methyl methacrylate polymer may be used as a substitute for glass with the advantages of reduced weight and brittleness; sheets .of poly'- styrene may be used where a support of high `Water resistance is required; andl flexible supports resembling rubber may be prepared from plasticized polyvinyl chloride. Syntheticcolloid materials are also of Vuse in modifying the properties of the more conventional supports. For example a fibrous cellulosic support such as paper, or a colloid lilm suppo'rt such as a cellulose or cellulose nitrate or cellulose acetate lm, may be made more resistant to Water by providing it with surface coatings of a composition containing a highly hydrophobic synthetic colloid such .as polystyrene or methyl methacrylate polymer, compare, for example, British Patent No. 513,238. v

However, when a gelatino photographic emulsion is coated directly on a hydrophobic colloid surface, the degree of adhesion effected is frequently insufficient for photographic purposes and it is therefore the practice, for example when coating a gelatine silver halide emulsion on cellulose nitrate or cellulose acetate film base, to provide a layer (known as a substratum) between the support andthe emulsion to secure good anchorage between the layers. 1

esteried alkyl methacrylate polymers by providing a substratum of an alkyl methacrylate polymer of lowerV degree of esteriiication, i. e.

containing more free carboxyl groups.

According to the present invention, therefore,

photographic elements arepr'ovided which comprise a support having a surface of a highly esteried (including fully esterified) alkyl methac- With supporting surfaces of synthetic hydrophobic colloids such as alkyl methacrylate polymer there is some difficulty in securing adequate j adhesion, and the types of substratum commonly used in securing adhesion of gelatino silver halide emulsions'to cellulose acetate and cellulose nitrate supports are not very suitable. I

' Alkyl methacrylate polymers vary in vconstituthe methacrylic acid residues, and it has now been discovered that gelatine photographic emulsions can be satisfactorily anchored to highly Vemulsion layer, coated on such rylate polymer, one or more substrate. containing alkyl methacrylate polymer of lesser de gree of esterication coated on said surface, and

a gelatine layer, e. g. a photographic gelatino on the outermost of such substrata.

More particularly the invention is concerned with the case where the alkyl methacrylate polymer is a methyl methacrylate polymer. v

Methyl methacrylate polymer as commercially available, e. g. as the product sold under the registered trade mark Diakon, fully esteriiled, i. e. it contains no freecarboxyl groups. Methyl methacrylate polymers containing some free carboxyl Vgroups may be prepared by the co -polymerlsation of methyl methacrylate and methacrylic acid in solution in a common solvent, for example methyl alcohol and benzene. by heating the solution in the presence of a polymerisation catalyst such as benzoyl peroxide. Another method, somewhat simpler, is to eect the partial hydrolysis of a fully esteried methy1 methacrylate polymer by means of acid or alkali. In' general acid hydrolysis in solution is preferred, 'and particularly hydrolysis by means of sulphuric acid.

`Methyl methacrylate polymer, for example that sold under `the registered trade-mark Diakon, may be dissolved in cold aqueous sulphuric acid containing up to 35% by volume of Water. The .polymer may then be hydrolysed by heating the solution. The degree of hydrolysis may be controlled -by regulating the proportion of sulphuric acid to water in the solution and the temperature and duration of the heating. While concentrated sulphuric acid maybe used for dissolving the polymer, the process is then somewhat more diilicult to control as the acid is 'liable to cause breakdown of the polymer strucv tion according to the degree of esterication of paired Elm-forming capacity. Generally speak.

ing a given degree of hydrolysis maybe achieved by employing a vhigh temperature and a short time of heating. 0r a lower temperature and a longer time. 'Ihe temperature and time are preferably chosen so as to allow of accurate repro-l ducibility from one batch to another. 'VI'he folsubstratum or Y is substantially lowing table ysis beingexpressed on indicates typical results obtained by sulphuric acid hydrolysis, the degree of hydrolthe basis that 100% hydrolysis represents complete conversion of the methyl methacrylate polymer to polymethacrylic acid. e

Acid mixture Tefmpexture Tim of hlr olentis o reac on reac on y ro ys Sulagilmo Water n Cc. Cc. C.

70 30 60 20 mins 2. 7 70 30 60 ll mins 4.7 70 30 70 60 mins l5. 3 70 30 70 150 mins 30. 9 100 Nil 20-25 4 days 67. 5

When the hydrolysis has reached the desired stage the polymer may be precipitated by pouring the solution into water, and the precipitate washed first with water and then with ethyl alcohol. The polymer may then be purified by redissolving it in acetone and repreciptating with water and may then be pressed free of entrained water and dried,-for example at.100 C.

With increasing degrees of hydrolysis, i. e.,

with increasing content of free carboxyl groups,

the solubility of the resin in common solvents varies progressively. Thus, whereas Diakon F is soluble in acetone, the partially hydrolysed products are increasingly less soluble in acetone as the degree 'of hydrolysis increases, so that, for example, a product hydrolysed to the extent of about 66% ls insoluble in pure acetone, though soluble in acetone containing 20% water, and a product hydrolysed to the extent of about 77% is insoluble in pure acetone, though soluble in acetone containing 50% water. The products are insoluble in water alone, though the more highly hydrolysed products swell in water.l The less hydrolysed products are insoluble in aqueous ammonla, but with increasing degree of hydrolysis beyond about 15% become soluble in aqueous ammonia.

IThe optimum degree of hydrolysis of the methyl methacrylate polymer to be used in the substratum must, of course, be selected withregard to the degree of esteriiication of the methyl methacrylate polymer surface on which it is to be coated and with regard tothe character of the gelatino emulsion layer which is to be coated on it. If the degree of hydrolysis is too little adhesion of the gelatino emulsion will not be wholly satisfactory, Whilst if the degree of hydrolysis is too great so that there is too wide a difference between the degree of esterification of the lsupporting surface and of the substratum adhesion between these two will not be whollysatisfactory. In general, with a supporting surface consisting of substantially fully esterined methyl methacrylate polymer and a normal gelatino silver halide emulsion, a substratum containing a methyl methacrylate polymer hydrolysed to the extent of 15 to 25% is satisfactory.

the support may be wholly composed of methyl mer. Other layers may be present in the support as desired providing that the surface` layer is a methyl methacrylate polymer. For example, a support having a basis of cellulose acetate may have ,a surface layer of cellulose nitrate, or a support having a basis of polyethylene may have a surface layer of polystyrene, and such surface layer may be coated with methyl methacrylate polymer.

Whilst the substratum may contain the methyl methacrylate polymer containing free carboxyl groups as the sole film-forming ingredient,` it is generally preferred to include in it a proportion of gelatin. If desired several substrata may be applied in succession, e. g. first a substratum containing methyl methacrylate polymer containing free COOH group as the sole film-forming ingredient, and then a substratum containing both the methyl methacrylate polymer containingr free COOH group and gelatin. If desired, this latter layer may be followed by, er substituted by, a substratum in which the sole film-forming colloid is gelatin; in this case the gelatin substratum coating solution should preferably contain a proportion of organic solventfor the methyl methacrylate polymer in the underlying substratum. A gelatino photographic emulsion layer may then be coated onvthe gelatin substratum.,

It will be appreciatedthat the methyl methacrylate polymers employed according to this invention should not be soluble in any processing solution, e. s. photographic developer, with which the final product may be treated.

The following examples illustrate the invention:

Example I A photographic support I as shown in Figure 1y of the drawing of paper was rendered more resistant to water by coating its surfaces with the following'solutlon: a

' Fully esterifled methyl methacrylate polymer (Diakon Dl gm l0 Toluene cc 75 Ethyl alcohol cc 15 These coatings 2 and 3 were dried and the following solution applied to form a substratum:

When the substratum d was dry a coating E of gelatino silver halide emulsion was applied. Exv -cellent adhesion was obtained between all the layers.

Example I1 A paper support 6 as shown in Figure 2 of the drawing was rendered translucent by passing it through the following solution, which was mainmethacrylate polymer, or supports primarily composed of other materials but yhaving a surface lcoating of methyl methacrylate polymer may be employed, for example the materials described in British Patent No. 513,238. Thus, for example, the support may consist of paper, or cellulose or cellulose derivative, lor hydrophobic colloids such as plasticised polyvinyl chloride or polystyrene,

coated with a layer of methyl methacrylate poly-` tained at a temperature of about C:

Polystyrene gm 30 Tri-cresyl phosphate cc 5 Xylene cc-- 65 The impregnated paper was dried and was The surface of the methyl methacrylate po1ymer layer l was then coated with the following solution to form a first substratum 8:

Methyl methacrylate polymer hydrolysed to the extent of 20%-` ;gm -10 Methyl ethyl lretone...I cc 1000 polymer of lower degree of esterification, and a gelatin emulsion layer.

What we claim is:

1. A photographic element which comprises a support having a surface of a substantially fully y esteriled methyl rmethacrylate polymer, at least Thesurface of this substratumwas then coated with the following solution to form a second sub- A coating I of gelatino silver halide emulsion was then applied to the surface obtained.- Excellent adhesion between all the layers'was thus effected.

l Example III A support l I as' shown in Figure 3 of the draw.. ing of plasticised polyvinyl chloride was coated with a 2% solution of a fully esteried methyl methacrylate polymer in methylv ethyl ketone and the surface of the coating I 2 was then rcoated with the following solution to forma substratum I8: l y

Gelatin agm" 5i Salicylic acid gm 2.5 Distilled water -cc-- 25 Methylalcohol i -cc- 125 Acetone cc 850 40% Formaldehyde cc-- 0.5 Methyl methacrylate polymer hydrolysed to the extent oi' 20% gm-- 4 After drying, the substratum was coated With a gelatino silver halide emulsion to form layer it. Excellent adhesion between the layers was obtained.

Whilst the invention has been described with particular reference to the coating of gelatino silver halide emulsion layers on the supports, it will be appreciated that other gelatina photographic layers may be coated on the supports with the assistance of the substrata of this invention, e. g. bichromated gelatin layers, as may also any plain, dyed or pigmented gelatin layers.

While-the invention has been described with particular reference to the coating of a gelatino emulsion layer on a support, it will be appreciated that the proceduremay be inverted. Thus a gelatine emulsion layer coated on a support may be supercoated first with va methyl methacrylate polymer oi low degree of esterication and then with a methyl methacrylate polymer of higher degree of esterication, Ihis form `of the invention has some value where it is desired to protect `one substratum layer adjacent thereto and having a methyl methacrylate polymer containing 15 to 25% free carboxyl groups, and a gelatino layer adjacent t'o said substratum layer.

2. A photographic element which comprises a support having a surface of a substantially fully esteried methyl methacrylate polymer, a substratum layer adjacent thereto containing gelatin and a methyl methacrylate polymer having 15 to 25% free carboxyl groups, and a gelatine layer adjacent to said substratum layer.

3. A photographic element which comprises a support having a surface of a substantially fully esterified methyl methacrylate polymer, a rst substratum layer adjacent Athereto containing a methyl methacrylate polymer having 15 to25% free carboxyl groups, a second substratum layer adjacent to the first containing gelatin anda methyl methacrylate polymer having 15 to 77% free carboxyl groups, and a gelatine layer adjacent to said second substratum layer.

4. A photographic element which comprises a support having a surface of a substantially fully esterified methyl methacrylate polymer, a iirst substratum layer adjacent thereto` containing a methyl methacrylate polymer having 15 to 25% free carboxyl groups, a second substratum layer adjacent to the ilrst containing gelatin and a an alreadyi'ormed photographic image, as in -V A methyl methacrylate polymer having 15 to 77% free carboxyl groups, a third substratum layer consisting essentially of gelatin, and a gelatino silver halide emulsion layer adjacent to said third substratum layer.

5. A photographic element which comprises a support having a surface of a substantially fully i esteried methyl methacrylate' polymer, at least one substratum layer adjacent thereto and containing a methyl methacrylate polymer having l5 to 25% free carboxyl groups, and a gelatino silver halide emulsion layer adjacent to said sub- 1 stratum layer.

6..A photographic element which comprises a support having a surface of a substantially fully esterifled methyl methacrylate polymer, a substratum layer adjacent thereto containing gelatin and a methy1 methacrylate polymer having 15 to 25% free carboxyl groups, and a gelatino silver halide emulsion layer adjacent to said substratum layer.

7. A photographic element which comprises a support having a surface of a substantially fully es teriiied methyl methacrylate polymer, a rst substratum layer adjacent thereto containing a methyl methacrylate polymer having 15 to 25% vfree carboxyl groups. a second substratum layer adjacent to the first containing gelatin and a methyl methacrylate polymer having 15 to 77% free carboxyl groups, and a gelatine silver halide emulsion layer` adjacent to said second substratum layer.

A JOHN ALFRED HENRY HART. EDWARD WILLIAM LEE. l 

